Pages 14.2 not opening previously saved file

I was working on a montage of photos and saved the file in pages format. When I returned to open it, Pages just hangs but with no activity, and I have to force-quit Pages. I have tried opening the file direct from the finder and from within the open Pages app. Because it was wip I hadn't reduced the images file size so the save file was about 30 MB.

And I had backups on TimeMachine, but those files, not surprisingly, also wouldn't open.

As I said, Pages 14.2, MacOS 15.0.1

any thoughts, suggestions welcome.

Many thanks,

John